/Engine/Plugins/MovieScene/MovieRenderPipeline/Source/MovieRenderPipelineCore/Public/MovieRenderTileImage.h
Grab a single pixel from the full res tile and scale it by the appropriate Scale value.
void FetchFullImageValue ( float Rgba, const [TArray](API\Runtime\Core\Containers\TArray)< float > & PlaneScale, int32 FullX, int32 FullY ) const